<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    html, body {
      margin: 0;
    }
    .tag {
      position: absolute;
      width: 50px;
      height: 50px;
      background-color: #333;
      transition: border-radius .1s;
    }
    .line {
      position: fixed;
      width: 1px;
      background-color: #000;
      left: 50%;
      top: 0;
      bottom: 0;
      transform: translate(-50%, 0);
    }
    .container {
      position: fixed;
      width: 200px;
      height: 300px;
      border: 1px solid #eee;
    }
  </style>
</head>
<body>

  <!-- <div id="container" class="container">
    <div id="tag" class="tag"></div>
  </div> -->

  <div id="tag2" class="tag"></div>

  <!-- <div class="line"></div> -->

  <script src="tag.js"></script>
  <script>
    // new Tag(document.querySelector('#tag'), {
    //   container: document.querySelector('#container')
    // })
    new Tag(document.querySelector('#tag2'))
  </script>
  
</body>
</html>